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Now Clare Holleley at the University of Canberra, Australia, and her team have discovered that this happens in the wild too. Of 131 lizards they caught, 11 females had ZZ chromosomes.

What’s more, the ZZ females laid almost twice as many eggs as ZW females. All of these eggs would be ZZ, since both the mother and father were. “They’ve lost a whole chromosome in one generation,” says Holleley.

The ZZ mothers also passed on a propensity to change sex&colon; their embryos switch from male to female at lower temperatures than eggs from ZW mothers. In fact, sex was determined solely by temperature, not chromosomes.

This means global warming could cause the sex switching to snowball – possibly putting the species at greater risk of extinction (Nature, doi.org/5zd).

This article appeared in print under the headline “Heat is on for sex-change lizard”